What the FDA labels say about taking them together
Diazepam and theophylline
Diazepam's FDA label (Valtoco) of June 3, 2026 names theophylline in its drug interactions section, and theophylline's label names diazepam too. The theophylline label: “25% increase Diazepam Benzodiazepines increase CNS concentrations of adenosine, a potent CNS depressant, while theophylline blocks adenosine receptors.”
Check it at the source: the diazepam FDA label on DailyMed (effective August 11, 2026, Waylis Therapuetics LLC); the theophylline FDA label on DailyMed (effective March 10, 2026, Strides Pharma Science Limited).
What does the diazepam label say about theophylline?
Valtoco label (Neurelis, Inc, June 3, 2026), drug interactionsMetabolism of Other Drugs Diazepam is a substrate for CYP2C19 and CYP3A4; therefore, it is possible that VALTOCO may interfere with the metabolism of drugs which are substrates for CYP2C19 (e.g., omeprazole, propranolol, and imipramine) and CYP3A4 (e.g., cyclosporine, paclitaxel, theophylline, and warfarin) leading to a potential drug-drug interaction.
Source: FDA drug label (Valtoco, NDA211635), Neurelis, Inc, effective June 3, 2026 (SPL set 1a8bcc90-68fa-474d-832c-0df01e825f39), via openFDA
Source: FDA drug label (Valium), Waylis Therapuetics LLC, effective August 11, 2026 (SPL set 260e2041-2bb3-482f-850e-b5d47a7bdbe6), via openFDA; the full label on DailyMed
What does the theophylline label say about diazepam?
Theophylline label, drug interactions25% increase Diazepam Benzodiazepines increase CNS concentrations of adenosine, a potent CNS depressant, while theophylline blocks adenosine receptors.
Source: FDA drug label (Theophylline), Strides Pharma Science Limited, effective March 10, 2026 (SPL set b7a90ccf-9c32-40cc-9008-7e55b3da4dfd), via openFDA; the full label on DailyMed
These are the labels' own sentences. PlainMeds does not grade interactions; a pharmacist or prescriber can say what they mean for one person's medicines.
Both medicines on the record
| Diazepam | Theophylline | |
|---|---|---|
| Labeled for | Anxiety, Muscle spasms and spasticity | Asthma |
| Boxed warning | Yes | No |
| Pharmacy cost (NADAC) | $0.0283 per tablet 10 mg tablet | $0.330 per tablet 300 mg tablet |
| Shortage now | No current entry | No current entry |
Source: FDA NDC Directory, CMS NADAC of October 7, 2026 and the FDA Drug Shortage Database (FDA files October 8, 2026)
What next?
- Check more medicines together
- up to five at once